Regulatory Position Statement – “Temporary Dewatering of Excavations to Surface Water”

7 Feb 2018


Earlier today, the Environment Agency published a new Regulatory Position Statement (RPS) entitled “Temporary Dewatering of Excavations to Surface Water.” This potentially has major implications for the disposal of water from construction sites as Dr. Richard Coulton, CEO of Siltbuster explains.

The statement sets out the circumstances under which water can be discharged off site without the need of a Bespoke Discharge Permit from the Environment Agency.   It states that contractors need a bespoke permit if they want to discharge off site into the surrounding environment – be that to surface water, groundwater or coastal/estuaries waters – for anything other than clean water (i.e. uncontaminated surface runoff/rain or ground water).  In particular, the guidance states that:


The discharge must:

  • be clean water, for example clear rainwater or infiltrated groundwater which has collected in the bottom of temporary excavations.
  • not result in water containing fine or coarse suspended solids (silty water) entering surface water
  • not last more than 3 consecutive months (the activity may stop and restart but the clock does not restart) – if the activity is likely to go over 3 consecutive months then a permit must be applied for
  • be made to surface water, such as a river, stream or the sea
  • have a method statement that minimises the risk of pollution


The discharge must not:

  • pollute surface water
  • contain any chemical dosing agents, flocculants or coagulants
  • be from a site which is contaminated by oil, metals, hydrocarbons, solvents or pesticides or other polluting substances
  • result in the spread of non-native invasive species, parasites or disease
  • cause flooding from surface water
  • cause erosion of the banks or bed of the receiving watercourse
  • contain concrete wash water even if it has been treated
  • contain site drainage from surface areas such as haul roads, storage or working areas
  • be from a site with naturally elevated concentrations of substances which exceed environmental quality standards


Before starting work on site you must:

  • plan how to minimise the level of contaminants such as silt entering the excavation
  • plan how to dispose of water that enters the excavation
  • plan not to use machinery in excavations while dewatering is taking place
  • minimise water entering the excavation, for example from rainfall, runoff, groundwater ingress or high water table
  • consider using sustainable urban drainage construction methods

Furthermore the discharge must not take place within 500m upstream of an Environmental Sensitive Area.


So what does all this mean?

The implications for the UK construction Industry are significant.

Firstly, the management of excess waters on site can no longer be managed on a reactive basis – construction companies must always now be proactive.  They must plan. They must plan how to minimise the level of contaminants (especially silt) from entering excavations and plan how to dispose of any waters entering excavations. They must plan their activity so that machinery and operatives are not working in areas where pumping operations are being carried out and they must plan the management of surface water runoff across the site.

Soils on most UK construction sites are not fines free (they contain silts and clays) and therefore, following the new guidance, water cannot simply be discharged off site. Most construction sites are now faced with the challenge of either applying for a Bespoke Permit, with treatment on site, or finding alternative (and potentially more expensive) disposal route, for example, either by tankering off site or discharge to sewer – which requires the prior approval of the local utility company.

The RPS also effectively makes the preparation of a Site Water Management Plan prior to commencing work, mandatory for all sites irrespective of whether a Bespoke Permit is required.  For those sites that require a permit, the plan is essential. The EA wants to see that the contractor has developed a robust water management plan for the site that:

  • Endeavours to minimise the risk and amount of contaminated water generated by isolating clear surface and groundwater as far as possible from the construction activities (for example by installing peripheral diversion channels, etc).
  • Isolates concrete wash water and potentially oil contaminated water (from fuelling and machinery maintenance areas) from the rest of the site.
  • Estimates the amount of contaminated water generated and puts in place suitable methods for treating it.
  • Includes contingency plans to cover the ‘what if’ scenarios.
  • Demonstrates adequate site operator training and awareness of the environmental issues associated with the risk of waterborne contamination
  • Documents the procedures put in place and provides documentary evidence of compliance with the water quality standards imposed by the Permit (in terms of volume of water treated and water quality).

It is widely known within the industry that obtaining environmental permits can take time and it can be very costly if plant and workers are stood down while such a permit is being processed.  That’s why it is imperative that contractors at the planning stage think through the best practical options for managing waterborne pollutants on construction sites and, where applicable, apply for the Bespoke Permit well in advance.


Act Now

Complying with these requirements clearly represents planning and a major increase in workload for engineering and environmental departments. It requires specialist knowledge of not only the proposed construction works but also the hydrology and appropriate methods of water treatment.

At Siltbuster we have been actively preparing the industry for this over the past few years through our inhouse training courses which have so far been attended by over 5,000 delegates. We have also given technical support to those involved in major infrastructure projects by providing specialist consultancy services needed to prepare site water management plans.

To ensure your projects don’t fall foul of the Environment Agency’s new position statement, book a place on our CPD accredited course “Prevention of Pollution on Construction Sites” or to arrange a bespoke technical training day tailored for your site specific activities call 01600 772256 or email


Siltbuster have released a Whitepaper on the new Dewatering Guidelines